SN54ACT8999

The SN54ACT8999 are members of the Texas Instruments SCOPEE testability integratedcircuit family. This family of components facilitates testing of complex circuit-board assemblies.

The SN54ACT8999 enhance the scan capability of TI's SCOPEE family by allowing augmentation of a system's primary scan path with secondary scan paths (SSPs), which can be individually selected by the 'ACT8999 for inclusion in the primary scan path. The SN54ACT8999 also provides buffering of test signals to reduce the need for external logic.

By loading the proper values into the instruction register and data registers, the user can select one of four secondary scan paths. SN54ACT8999 has the effect of shortening the scan path to allow maximum test throughput when an individual subsystem (board or box) is to be tested. Any of the SN54ACT8999's six data registers or the instruction register can be placed in the device's scan path, i.e., placed between test data input (TDI) and test data output (TDO) for subsequent shift and scan operations.

All operations of the SN54ACT8999 except counting are synchronous to the test clock (TCK). The 8-bit programmable up/down counter can be used to count transitions on the device condition input (DCI) and output interrupt signals via the SN54ACT8999 condition output (DCO). The device can be configured to count on either the rising or falling edge of DCI.